RE: cola, allcola problem

From: Matson, Robert (
Date: Thu Jan 31 2002 - 09:42:33 EST

  • Next message: Matson, Robert: "RE: sat decay"

    Hi Tristan and List,
    > I am trying to predict some satellite encouters with the Cola
    > and Allcola programs but I am always getting the following
    > message:
    > 'Convergence problem with #xxxxxx: orbits may coincide.
    > Anyone got the sollution ?
    As some other list members have suggested, this can happen when
    physically linked satellites (e.g. the various elements of ISS)
    each have their own TLEs.  The differences in the orbits are
    small, but non-zero, so they slowly drift apart.
    However, I'm sure Tristan is aware of this and probably ignores
    convergence errors that are reported for physically connected
    satellites.  He's correct:  I've noticed this error still comes
    up at times between apparently unrelated objects.  Bjoern Gimle
    has mentioned this problem to me on several occasions, but I
    haven't had time to dig into the code to see what it is about
    these orbits whose comparative differences cause COLA (and
    ALLCOLA) problems.
    If I find a solution (even a partial one) I'll certainly post
    an update.
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